The EPW9 is an emergency power off push button that turns off the UPS in the event of a problem. APC explains...
APC’s Emergency Power Off (EPO) System consists of one or more wall-mounted, push-button EPO
boxes. Each EPO box provides a single point of equipment shutdown for up to eight APC InfraStruXure
devices and one third-party device (such as an upstream breaker), using Normally Open (NO) contact
closure connections. You can cascade an EPO box with other EPO boxes to support multiple points of
equipment shutdown.
While EPO is good and required thing...Why you would pay $1200, when this mushroom plunger switch does the same thing is beyond me. But thats why APC makes billions of dollars and I still eat ramen noodles.
